1. Field of the invention
The present invention relates to a battery checking method and battery checking device using the same, particularly, a method and a device for checking whether a battery is fully charged or not.
2. Description of the Related Art
Recently, various rechargeable batteries such as lead-acid battery, nickel-metal hydride (Ni-MH) battery and the like have been used for electric vehicles, and it has become important to determine whether such batteries are fully charged or not. Usually, the battery's full charge is determined according to the following conditions:
1) when a rate of temperature change dT/dt becomes a threshold level as disclosed in JP-A-6-290816,
2) when a rate of voltage change dV/dt becomes a threshold level,
3) when the battery terminal voltage becomes a threshold level as disclosed in JP-A-8-140283, or
4) when a difference between battery temperature and outside temperature becomes a threshold level as disclosed in JP-A-6-290816.
However, the rate of temperature change dT/dt and the rate of voltage change dV/dt change easily if the charging current or type of the charging circuit changes. The battery terminal voltage changes significantly with types and variations of batteries. The difference between the battery temperature and the outside temperature also changes if the outside temperature changes considerably. Thus, it is difficult to determine the battery's full charge accurately by one of the above-stated methods.